The SIK Axis and Pulmonary Oxidative Defense: Selenium Deficiency, Selenoprotein Depletion, and NRF2 Insufficiency as Upstream Determinants of Vulnerability Across Major Respiratory Diseases

The lung is the organ most continuously exposed to environmental oxidants. It maintains functional integrity through a multi-layer antioxidant defense system anchored by four selenium-dependent glutathione peroxidase isoforms. This paper proposes that selenium adequacy and NRF2 functional status are rate-limiting upstream determinants of pulmonary oxidative defense capacity across COPD, idiopathic pulmonary fibrosis, asthma, and acute respiratory distress syndrome. The GPx4-ferroptosis-IPF axis is identified as a mechanistically complete pathway from nutritional selenium status to pulmonary fibrosis progression. All claims are hypothesis-level requiring prospective clinical confirmation.